As written, there's no way to incapacitate someone with non-lethal damage and once you are unconscious there's no risk of dying from your wounds.
Non-lethal damage: Non-lethal damage affects vigor normally. Once vigor is zero track it as virtual wounds that only affect consciousness. If you are "wounded" due to these virtual wounds you need to make the Fortitude save to stay conscious but you don't lose additional wounds. If the total of wounds + non-lethal is equal to total wounds you fall unconscious.
Stabilization: If you are wounded and unconscious you will bleed out (losing 1 wound per round) unless you can make a DC 10 Constitution check with penalty equal to your wounds below your wounding threshold.